Phenolic compounds which have an alkyl substituent in the ortho position on the ring are known to be useful as starting materials for the preparation of polyphenylene oxide (ether) resins. In general, such compounds are made by processes involving the vapor phase reaction of a phenolic compound and an alkyl alcohol in the presence of a catalyst. Various catalysts have been described in the patent literature.
For instance, processes for the ortho-methylation of a phenolic compound using magnesium oxide as a catalyst are disclosed by Hamilton in U.S. Pat. Nos. 3,446,856 and 3,479,410. Hamilton teaches that the magnesium oxide can be derived by the thermal decomposition of magnesium carbonate, basic magnesium carbonate or magnesium hydroxide. Van Sorge in U.S. Pat. No. 3,972,828, describes a catalyst consisting of powdered magnesium oxide in combination with an inert polymeric binder.
Still other catalysts are disclosed elsewhere in the patent literature. U.S. Pat. No. 3,873,628 describes a catalyst prepared by forming a mixture of magnesium oxide and manganese sulfate, heating to nearly complete dryness, and calcining at an elevated temperature to achieve activation. The mixture can be prepared using finely divided powders of the two compounds, or from an immersion of the magnesium oxide in an aqueous solution of manganese sulfate. Both U.S. Pat. Nos. 3,972,836 and 3,974,229 (also to Van Sorge) describe ortho-alkylation processes in which the catalyst comprises a mixture of magnesium and manganese oxides. In a preferred procedure, the catalyst is activated for use by heating it in the reactor in the presence of methanol vapor, prior to commencement of the alkylation reaction.
More recently, an ortho-alkylation process has been disclosed in which a catalyst comprising a magnesium compound is activated by calcining at an elevated temperature, in situ, in the presence of a feed stream of the alkylation reaction mixture. This is described in U.S. application Ser. No. 303,567, filed Sept. 18, 1981, belonging to the same assignee as herein.